1. Field of the Invention
The present invention relates to a modulating and demodulating method and a transmitting method of a control apparatus and a control apparatus using thereof which is preferably applied to a case in which a wireless communication network or the like is constructed by utilizing infrared ray or the like. In details, when communication is carried out between an apparatus on the controlling side (control node) and an apparatus on the controlled side (controlled node) which function as terminals of wireless communication, modulation sets adopting the same kind of a modulation system having different multiple value formation levels are prepared and an optimum modulation system is selected in accordance with communication distance or communication speed flexibility in respect of participation in a wireless communication network can be provided under more pertinent circuit scale.
Further, when optical transmission is carried out as a wireless communication, in obtaining reception data by receiving an optical signal outputted from a transmitter, the optical signal which is delayed is restricted such that a bit error rate thereof is not deteriorated more than a predetermined bit error rate by which adverse influence of the delayed optical signal is avoided and transmission of data can be carried out at high speed and excellently.
2. Description of the Related Art
In recent years, with progress of spread of portable devices, wireless formation of various analog and digital interfaces is promoted. Particularly, in the field of computer, wireless formation and high speed communication are intensively carried out, for example, by using technologies represented by wireless LAN (local area network) and IrDA (infrared data association), construction of a network (wireless network) by noncontact connection has been progressed not only between portable devices (communication devices or the like) disposed in the same room but also between a portable device and an installed device (television receiver or the like).
According to the wireless network, there is constructed a network in which one device constitutes a parent node (control node) and remaining one or more of devices constitute child nodes (controlled nodes) and communication between the parent node and the child nodes is connected by optical communication utilizing infrared ray or the like.
FIG. 1 shows a case in which a wireless communication network is constructed by one parent node 10 and one or more, three in this example of child nodes 20 (20A, 20B and 20C). Means (transmitting means and receiving means) for carrying out optical communication by infrared ray are installed at insides of the respective nodes 10 and 20. The child node 20 can communicate with only the parent node 10 by carrying out communication in synchronism with each other by using infrared ray.
When such a network for wireless communication is constructed, as a modulation system used in communication between the respective child nodes 20 and the parent node 10, the following cases are conceivable.
(1) The same modulation system is adopted for the parent node 10 and the child nodes 20.
(2) The respective nodes adopt different modulation systems.
Meanwhile, the following problems are conceivable in the above-described wireless communication means. That is, when the system (1) mentioned above is adopted as a communication system in carrying out data communication in order to simplify communication control and reduce the circuit scale as less as possible, the communication control is simplified since the same modulation system is adopted in the respective communication, however, transmission speed and communication distance between the nodes are fixed by the adopted modulation system and accordingly, a communication system which is devoid of flexibility is constituted.
Therefore, in order to carry out higher speed communication, the problem cannot be dealt with unless the modulation system is changed and when lower speed communication is sufficient, a wasteful equipment is provided. Because the circuit scale cannot be reduced.
Further, according to the system (2), when different modulation systems are adopted in communication between respective nodes such as between the parent node 10 and the child node 20A or the parent node 10 and the child node 20B, in the respective child nodes 20A, 20B and 20C, synchronizing circuits in correspondence with the modulation systems used by the respective child nodes become necessary and further, the communication control is also complicated.
Further, when transmission of data is carried out by using an optical signal of infrared ray or the like, on the reception side, as shown by FIG. 2, a direct signal from the transmission side and an optical signal which is delayed by being reflected by a reflecting object are supplied. Therefore, multiple paths are caused by a direct signal shown by FIG. 3A and a reflected signal (ghost signal) shown by FIG. 3B in which the signal level of the direct signal is attenuated and the signal is delayed and a reception signal shown by FIG. 3C is outputted from the reception side.
In this way, the signal waveform of the reception signal is changed by reflection of the signal and accordingly, S/N ratio (signal to noise ratio) is deteriorated, when the data transmission speed becomes fast, influence of the change in the signal waveform is significant and data cannot be transmitted correctly.
Therefore, in order to remove such an adverse influence by the multiple paths, for example, there is carried out a processing in which in starting data transmission, predetermined data is transmitted and received, influence of multiple paths is confirmed and adverse influence of multiple paths is removed from a reception signal in data transmission thereafter. However, according to a method of using so-to-speak adaptive automatic equalization where data transmission is carried out correctly by removing influence of multiple paths, circuits for removing influence of multiple paths are added and load of signal processing for removing influence of multiple paths is increased.
Hence, it is an object of the present invention to be able to construct a wireless communication network without excessively enlarging circuit scale and which is rich in flexibility by being able to select a pertinent modulation system in accordance with communication distance and communication speed.
Further, it is an object of the present invention to provide an optical transmission method and an optical transmission apparatus capable of transmitting data at high speed and excellently by precisely and simply restricting multiple paths.
In order to resolve the above-described problems, according to one aspect of the present invention, there is provided a modulating and demodulating method of a control apparatus, wherein in a wireless communication network in which one or more of controlled control apparatuses are present in respect of one control apparatus and mutual communication is carried out between the control apparatus and the controlled control apparatuses by using infrared ray or the like, modulation sets comprising a same kind of a modulation system having different multiple value formation levels are prepared for the controlled control apparatuses, a modulation system is selected from the modulation sets in accordance with communication distance and communication speed necessary for the controlled control apparatuses and a signal is modulated by using the selected modulation system.
According to another aspect of the present invention, there is provided a control apparatus, wherein in a wireless communication network in which one or more of controlled control apparatuses are present in respect of one control apparatus and mutual communication is carried out between the control apparatus and the controlled control apparatuses by using infrared ray or the like, the controlled control apparatuses are respectively installed with modulating means and demodulating means of a signal, the modulating means are prepared with modulation sets comprising a same kind of a modulation system having different multiple value formation levels, a modulation system determined in accordance with communication distances and communication speeds necessary for the controlled control apparatuses is selected from among the modulation sets and the signal is modulated by using the selected modulation system.
According to the present invention, the modulation sets comprising the same kind of the modulation system having different multiple value formation levels are prepared for child nodes which are the control apparatuses on the controlled side. The parent node which is the control apparatus on the controlling side periodically transmits control blocks by using modulation having a lowest multiple value formation level among the modulation sets. The modulation system having the lowest multiple value formation level is utilized in consideration of the fact that a child node capable of carrying out communication only by the communication system having the lowest multiple value formation level participates in the wireless communication network.
By contrast, according to the modulation system used in the child node, the multiple value formation level is selected in accordance with a priority in the communication distance and the communication speed.
For example, when a child node which has a priority in the communication speed over the communication distance communicates with the parent node, the modulation system having a comparatively high multiple value formation level is adopted from among the modulation sets. By contrast, when a child node which has a priority in the communication distance over the communication speed communicates with the parent node, the modulation system having a comparatively low multiple value formation level is adopted from among the modulation sets. Therefore, the parent node is provided with the demodulating means capable of demodulating all of the modulation systems which can be selected by the child nodes.
Further, according to an optical transmission method of the present invention, transmission and reception of the optical signal is carried out while restricting an optical signal having a large delay amount than a delay amount of an optical signal which is delayed when the delayed optical signal is received and the reception data constitutes a predetermined bit error rate.
Further, according to another aspect of the present invention, there is provided an optical transmission apparatus comprising transmitting means for transmitting an optical signal based on transmission data, receiving means for providing reception data by receiving the optical signal outputted from the transmitting means and optical restricting means for restricting the optical signal supplied from the transmitting means to the receiving means by being delayed by more than a predetermined delay amount. Further, the transmitting means includes modulating means for distributing the transmission data and carrying out quadrature modulation by using the distributed transmission data and signal outputting means for transmitting the optical signal based on the transmission signal provided by the modulating means, the receiving means includes demodulating means for forming reception data by demodulating a signal provided by receiving the optical signal and the optical restricting means restricts the optical signal having a delay amount larger than a delay amount of the optical signal which is delayed when the delayed optical signal is received and the reception data constitutes a predetermined bit error rate.
According to the optical transmission method and the optical transmission apparatus, when the optical signal outputted from a transmitter is received and the reception data is provided, the optical signal having a delay amount larger than a delay amount of the delayed optical signal is restricted at the predetermined bit error rate by restricting a radiation angle or a light receiving angle of the optical signal by optical signal restricting means of, for example, a light blocking tube, an optical lens or the like such that the bit error rate is not deteriorated more than the predetermined bit error rate.